The present invention relates to an electric drive system having a multi-phase electric machine, multiple electrical power output stages, and control units, which are connected to the electrical power output stages, for controlling and/or regulating the electric machine. Preferably, the electric machine is a component of a drive train for a motor vehicle, in particular for a motor vehicle having at least two different drive units, such as an internal combustion engine and an electric machine.
Electric machines for drive tasks are equipped with electronic controllers, which regulate the speed and power of the machine. Three-phase and two-phase multi-phase machines of various pole pair counts and DC current machines are the most widespread drives. Furthermore, machines having more than three-phase systems are known. All drives share the feature that for optimal exploitation of the drive, the electronic controllers and the electric machines must correspond in the number of phases.
Typical machines and controllers have a concentrated system structure (see FIG. 1), i.e., the number of the individual electrically executed phases and/or poles of the controller corresponds to the number of magnetically differentiable phases of the electric machine. To adapt the current and voltage between the power system and the electric drive, and for reasons of electric controllability, control elements and/or phases of the machines are connected in parallel or in series.
For complex drive tasks in traction and/or in automation technology, the drives are partially operated permanently or temporarily in parallel, i.e., they generate a joint torque output.
In addition, electric machines are known for hybrid drives, in which the execution as concentrated drives is dispensed with for reasons of installation space exploitation. For example, the power output stages of the electronic controller are situated as segments on the mantle of the electric machine for these drives. In a further embodiment, the segments are assigned as so-called half-bridges to individual phases of the electric machine. The separate activation of individual windings of electric machines using full bridges (H-bridge circuit) is also known. Embodiments of this type are known, for example, from DE 198 17 333 C1 or DE 101 12 799 C1.
In mobile drive technology, electric machines having inverter power are increasingly integrated in the drive train of a motor vehicle. The electric machines are frequently implemented as permanently excited synchronous machines, in which the terminal voltage of the electrical machine is sometimes higher than desired, which is problematic. The elevated terminal voltage is counteracted, for example, by the operation of the electric machine using field weakening. A current is applied using a regulating method, which has the result that the magnetic field active in the air gap is reduced. Alternatively or additionally, braking resistors (so-called brake choppers) may be used, excess electrical energy being converted into heat using an ohmic resistor. Alternatively or additionally, the excess energy may also be fed back in a targeted manner into an energy accumulator. However, these measures are only advantageous in a limited way. In the event of so-called field weakening, a controller breakdown may occur, by which the terminal voltage of the electric machine would again rise undesirably. Additional components are required for limiting the terminal voltage using braking resistors. An energy accumulator is necessary for the feedback of the excess electrical energy present because of the increased terminal voltage, for which it is ensured that it is always capable of absorbing the excess energy.
The present invention is based on the object of providing an electric drive system, by which the above-mentioned disadvantages are overcome. In particular, through the present invention, emergency operation of the electric machine is to be possible in the event of malfunction or breakdown of a control unit. The object is achieved according to the present invention by providing an electric drive system having a multi-phase electric machine, multiple electrical power output stages, and control units, which are connected to the electrical power output stages, for controlling and/or regulating the electric machine. At least two control units are provided for controlling and/or regulating, and each such control unit is assigned to at least one power output stage group.
High flexibility of the electric machine in regard to its controller and also increased security from breakdown are ensured by the use of multiple units for controlling and/or regulating (referred to in the following as control units) the electric machine and the assignment of control units to a power output stage group to switch at least one supply phase of the electric machine. A multipart electric machine (electrical machine having multiple integrated partial machines) is more or less provided by the present invention, in which each machine part (or each integrated partial machine) may be controlled and/or regulated autonomously. The partial machines, are preferably, partial stators, which act on a shared rotor.
The regulation of the overall drive is also partitioned and assigned to the individual partial motors. The drives are synchronized with one another by a higher-order setpoint value preset in particular, which distributes the setpoint value for the overall drive to the individual drives, and by the synchronization of the processor clocking of the individual controllers.
The synchronization of the individual drives, for example, via a master and subordinate slave controllers, is also specified as a further embodiment.
In another refinement, it is possible that master or slave regulation is not assigned directly to any electric machine, but rather the master or slave regulation and/or the control unit assigned to the electric partial machine is only used for processing measured and regulating variables. This is the case if multiple electric machines are already present, which ensure reliable partial operation of the system. It is then contemplated that further partial machines are provided, to which a passive control unit is solely assigned in such a way that it solely processes measured and regulating variables—but does not actively activate the partial machine assigned thereto.
In this way, on one hand emergency operation of the machine is ensured if the control unit assigned to a partial machine breaks down, and on the other hand every machine part may be controlled individually. For example, one machine part may be temporarily operated as a motor, while another machine part is operated as a generator—arbitrary activations are contemplated here.
In a preferred embodiment of the present invention, the (divided) electric machine is implemented as a multiphase electric machine (e.g., 2×3 phases), in which a power output stage (e.g., in the form of a power half-bridge) is assigned to each phase and a separate control unit (e.g., current regulation) is assigned to each of the two power output stage groups comprising three power output stages.
Through this construction according to the present invention of a (multipart) electric machine, a redundancy is provided which allows, in the event of breakdown or shutdown of one or more power output stages or one or more control units, the electrical machine to operate further via the remaining power output stages and/or the remaining control units and associated power output stages.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.